Oral Poster & Poster Presentation 9th Australasian Virology Society Meeting 2017

The host anti-viral protein viperin positively augments the innate immune response against DNA viruses (#109)

Keaton M Crosse 1 , Kylie Van der Hoek 2 , Ebony A Monson 1 , Monique L Smith 2 , Michael R Beard 2 , Karla J Helbig 1
  1. Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, VIC, Australia
  2. Department of Molecular and Cellular Biology, Research Centre for Infectious Diseases, University of Adelaide, Adelaide, SA, Australia

We have previously shown that viperin is able to restrict many prominent viral pathogens including HCV, HIV, ZIKV and DENV. The extent of viruses susceptible to viperin ranges across multiple viral families, encompassing vastly divergent viruses. Multiple mechanisms have been described for viperin’s widespread anti-viral properties, the latest of which is its ability to positively augment immune signalling pathways. Viperin has been shown to augment TLR7 and TLR9 signalling pathways in murine plasmacytoid dendritic cells, which increased production of the potent anti-viral cytokine, interferon. Here we shown for the first time, that viperin also plays a role in positively augmenting the dsDNA signalling pathway. Through the combination of luciferase and RT-qPCR with ectopic expression of viperin, we were able to demonstrate that viperin enhances the activity of the IFN-b promoter by approximately 15 fold in the presence of dsDNA stimulation in both Huh-7 and HeLa cell lines. The utilisation of various viperin mutants demonstrated that viperin requires not only its characteristic lipid droplet localisation to augment dsDNA signalling, but also requires additional sequences within this region of the protein. Confocal microscopy in Huh-7 cells following dsDNA stimulation revealed that viperin co-localised with key signalling molecules of this pathway, STING and TBK1, as well as ubiquitin ligases, TRAF6 and TRAF3, which was confirmed using proximity ligation assays. Subsequent immunoprecipitation assays with Huh-7 cells revealed a physical interaction between viperin and STING, and demonstrated that viperin expression enhanced the K-63 linked ubiquitination of TBK1 following dsDNA stimulation, which was also evident in primary murine embryonic fibroblasts. Viperin’s ability to augment the dsDNA innate immune response pathways may in part explain its capacity to restrict multiple viral families highlighting the key role this host protein plays in eliminating many prominent viral pathogens.